The sections above should handle the majority of requirements in using XSTAR. However, there is a set of hidden parameters defined during XSTAR's development that might be of use in many cases. Changing these parameters requires a slightly better understanding of the operation of the code. Note also that the parameter file formalism allows these parameters to be prompted along with the others, simply by changing the `h' to an `a' in the third field of the respective line of the parameter file.